Reversible cross-linking of cellulosic fabrics

ABSTRACT

CELLULOSIC FABRICS ARE DIETHYLAMINOETHYLATED AND/OR CARBOXYMETHYLATED AND THEREAFTER HEATED AT ELEVATED TEMPERATURES UNDER VACUUM FOR EXTENDED PERIODS OF TIME TO FORM CROSS-LINKS WHICH MAY BE REMOVED BY TREATMENT WITH STEAM OR ALKALINE SOLUTIONS.

United States Patent 3,567,358 REVERSIBLE CROSS-LINKING 0F CELLULOSIC FABRICS Donald M. Soignet, Metairie, and Ruth R. Benerito and John D. Guthrie, New Orleans, La.,. assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Aug. 29, 1969, Ser. No. 854,293 Int. Cl. D06m 13/20, 13/34, 13/54 US. Cl. 8116 6 Claims ABSTRACT OF THE DISCLOSURE Cellulosic fabrics are diethylaminoethylated and/or carboxyrnethylated and thereafter heated at elevated temperatures under vacuum for extended periods of time to form cross-links which may be removed by treatment with steam or alkaline solutions.

A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

An object of this invention is to produce cellulosic fabrics of high crease resistance. A further object of this invention is to produce a fabric that can be cross-linked and then the cross-links can be broken in a simple operation.

It is well known in the art that cellulose will react with many reagents through its hydroxyl groups. A reagent that can react with more than one cellulosic hydroxyl can form bonds between the different cellulosic chains and thus produce cross-linking. Many of the bonds formed can be broken by further chemical action. However, the reagent used to form the bond originally is usually destroyed or removed from the area of the cellulosic chain by the cross-link-breaking reaction. Hobart et al. [T ex. Res. 1., 36, 30(1966); Tex. Res. 1., 37, 380(1967); Tex. Res. J., 35, 353(1965)] have shown that cross-links could be broken. However, this process involved the immediate formation of new cross-links. Tesoro, et al. [J Appl. Polymer Sci., 12, 638(1968)] has been successful in breaking cross-links in treated fabrics but when these cross-links are introduced in the fabric a second time, they are not as efficient as the original cross-links.

By the process of this invention, cross-links can be introduced in a cellulosic fabric; they can be removed and at a later time reintroduced without any noticeable loss of efiiciency.

In the preferred process of this invention, a cellulosic fabric is modified to contain amine groups and further modified to contain carboxymethyl groups. The fabric is then dried in vacuo and the water originally bound in the cellulose to the amine, the acid and the cellulose hydroxyls are removed and a hydrogen bond is formed between the acid and the amine or the acid and the hydroxyl. This hydrogen bond can be removed only by the addition of water under pressure and temperature or by the application of a dilute base which converts the acid to the salt form. The latter is incapable of forming the strong hydrogen bond needed to produce cross-linking. To reintroduce cross-links into the fabric where the original cross-links were broken by the addition of water, it is only necessary to remove the bound water by heat and vacuum. Where the cross-link was broken by addition of a dilute base, it is necessary to convert the salt of the acid to the free acid and then remove the bound water by heat and vacuum.

The materials to which the process of this invention may be applied include any solid cellulosic material in the form of fiber, yarn, or fabric. Cotton, rayon, jute, and flax are suitable starting materials.

The following examples illustrate but do not limit the scope of this invention.

EXAMPLE 1 r a wet wrinkle recovery of 252 W-i-F (an increase in 88 W+F). There was a net loss of 1.01% H O.

EXAMPLE 2 Cotton fabric was modified to a degree of substitution of .06 with respect to nitrogen with Z-aminoethylsulfuric acid according to the method of Guthrie (Tex. Res. J. 17, 626, 1947). It was further modified with chloroacetic acid to an additional degree of substitution of .02. After curing in a vacuum oven at 140 C., a total pressure of 0.05 mm. Hg, and then air equilibrating, the fabric possessed a dry wrinkle recovery value of 266 W+F (an increase of W-i-F) and a wet recovery value of 254 W+F (an increase of 34 W+F). There was a net loss of 0.69% H20.

EXAMPLE 3 Cotton fabrics modified first with chloroethyldiethylamine hydrochloride to contain .4% nitrogen and then treated with chloroacetic acid to a carboxyl content of 5.5% were cured at 0.05 mm. Hg for 18 hours at various temperatures. Results of the curing are shown below.

Crease recovery Cure temperature, 0. Wet Dry 3 EXAMPLE 5 Wrinkle recovery angles 'i- Conditions temp., 0.

Solution type 0.05 N N aOH iSfiligion composed of 50 ml. of commercial bleach (Clorox) in 400 m z 2 DEAE-CM-cotton cured at, 150 0. and total pressure of 0.05 mm; Hg for 18 hours.

EXAMPLE 6 Cotton fabric from Example 5 that had been treated with .05 N NaOH showed that the IR band at 5.80 originally present and attributed to the C- stretch in the COOH group, had disappeared and a new band, at 6.2,u, attributed to the C-0 stretch in the COO group was present. 'Attempts to recrosslink the fabric by the application of heat and vacuum were unsuccessful. After soaking the fabric in .1 M CH CO H and then washing, thejabsorption band at 5.8 reappeared and subsequent heat and vacuum produced a cross-linked fabric. The ability of other acids to convert the fabric from Example to the free acid form can be regarded as the ratio of optical density at 5.75 (COOH form) to that at 6.25 0. ((300 form). This data is tabulated below.

Optical density N Fabrics were creased on a steam press to 90 p.s.i. pressure, some were placed in a vacuum oven at 155 C. and 0.05 mm. Hg total pressure for 18 hours. The creases are rated according to the AATCC test method 88C-1964T. Some fabrics with creases are washed in a home washer and other soaked in .05 N NaOH for 1 hour, Washed to remove excess NaOH then ironed flat. Fabrics included (1) one first treated with 2 chloroethyldiethylamine HCl then chloroacetic acid, (2) only 2 chloroethyldiethylamine HCl, (3) only chloroacetic acid, and (4) an unmodified control. Results are tabulated below. A value of 5 represents the greatest crease and a value of 1 the least crease.

Crease rating 1 Samples process washed in an automatic home washer on washwea cycle with Triton X-lOO and tumbled dry.

4 EXAMPLE 8 In step 1, the cotton fabric was first modified with 2 chloroethyldiethylarnine HCl to a nitrogen content of 0.4% then treated with chloroacetic acid to a carboxyl content of 5.5%. The fabric was then cured (step 2) at 155 C. and total pressure of 0.05 mm. Hg for 18 hours. In step 3, the fabric from step 2 is autoclaved under 26 p.s.i. steam pressure at 132 C. for 3 hours. In step 4, the fabric from step 3 is cured again at 155 C. and total pressure of 0. 05 mm. Hg for 18 hours.

Results are tabulated below.

Moisture Wrinkle recovery, content, Step dry per-sent EXAMPLE 9 Cotton fabrics as described in step 1 of Example 8 are cured at 0.'05 mm. Hg for 1 hour at various temperatures. Results are tabulated below.

1. A process for imparting durable creases and wrinkle recovery properties to a cellulosic fabric comprising carboxymethylating the fabric and thereafter heating the fabric under vacuum for an extended period of time at a temperature greater than the normal boiling point of water to remove bound water and promote bonding between carboxyl and hydroxyl groups therein.

2. A process for breaking bonds in a fabric prepared by the process of claim 1 which comprises treating said fabric at an elevated pressure with super-heated steam.

3. A process for breaking bonds in a fabric prepared by the process of claim 1 which comprises treating said fabric 'with a dilute base to convert carboxyl groups therein to the salt form.

4. A process for imparting durable creases and wrinkle recovery properties to a cellulosic fabric comprising carboxymethylating and diethylaminoethylating the fabric and thereafter heating the fabric under vacuum for an extended period at a temperature greater than the normal boiling point of water to remove bound water and promote bonding between carboxyl and hydroxyl groups and carboxyl amine groups therein.

5. A process for breaking bonds in a fabric prepared by the process of claim 4 which comprises treating said fabric at an elevated pressure with super-heated steam.

6. A process for breaking bonds in a fabric prepared by the process of claim 4 which comprises treating said fabric with a dilute base to convert carboxyl groups therein to the salt form.

References Cited Tesoro et al.; Journal of Applied Polymer Science, vol. 12, pp. 683697 (1963).

GEORGE F. LESMES', Primary Examiner I. CANNON, Assistant Examiner US. Cl. X.R.

2 Fabrics soaked in 0.05 N NaOH for 1 hour, washed to remove excess 8 116 2 38 144 NaOH, and ironed flat. 

